Alonso with AM 2+1 so, he has 1 year left with AM. Honda going to supply engine for AM in 2026. Alonso will not stay with AM in 2026. The driver market will wind up in 2024 itself.
Once Honda with AM, Honda will try to put his driver along side with Stroll Jr. Hence Alonso will not be in AM in 2026.
The only option Alonso has is jumping the ship in 2025 with 2+1 . The option he has is:
1. RB -> but I doubt because he already had bad experience with Honda when they return to F1 with McLaren. Ford is new so He will not move to RB in 2025
2. Mercedes -> it is he only and best option available for him. It is best to move to Mercedes with 2+1 so he will be driving till 2027 then retire from sports at the age of 46. It is the best option for Alonso
else,
retire from F1 in end of 2025 which I doubt because he will explorer 2026 rule change.